About Virtual Nebraska

Virtual Nebraska emerged out of the Consortium for the Application of Space Data to
Education (CASDE) project which began in September 1995 after Senator Bob Kerrey
challenged personnel of the Jet Propulsion Laboratory
(JPL) to find a better way to apply NASA's space data holdings to education.
CASDE's primary objective is to utilize NASA's legacy of data, information, and
technology to stimulate and challenge K-12 students to acquire and use scientific,
mathematical, and other skills. Project partners are the University
of Nebraska-Lincoln (UNL), JPL, and the University
of Nebraska-Omaha (UNO).

Virtual Nebraska serves as the prototype state for one of CASDE's key
objectives ~ Virtual America. It integrates CASDE data sets, imagery, tutorials,
tools and information under one umbrella, thus serving as the mechanism that allows users
to browse data without being preoccupied with the nuances of tools and esoteric data
formats.

In general, Virtual Nebraska is an on-line archive of satellite imagery and
aerial photography that gives users the opportunity to view the State's landscape
from unique perspectives (e.g., at infrared or microwave wavelengths). Additionally, this
web site offers digital elevation data, learning activities, image-processing tools,
historical "looks" at over 600 cities, and examples of how remotely sensed data
can be used to solve problems. We encourage you to use Virtual Nebraska to study
the State's geography, learn about the history of your city, locate your school,
monitor vegetation patterns throughout a growing season, or map the statewide distribution
of snow cover in January.

Who should use Virtual Nebraska?

Although Virtual Nebraska grew out of an education project, use is encouraged by
everyone. We have discovered that many people access this site simply to "see"
what their city, county, or region looks like from above. Recognizing familiar locations,
investigating "strange" shapes and colors, or identifying one's home or
farm can be fun and challenging. So, take some time and "click around". We
suspect that you will discover things you never knew about Nebraska.

It is also worth noting that data provided through this web site have been utilized by
professional agencies, businesses and agricultural producers across Nebraska. Soon
after the first version of Virtual Nebraska was published we began receiving
requests for imagery and related data from engineers, architects, planners and others
throughout the region.

How are the Data in Virtual Nebraska Prepared?

The data posted on this site were derived from a number of sources and sensor
types. The amount of preparation involved is dependent upon a number of variables. Below
are short descriptions of how the image data products were prepared for delivery over the
web.

All Data

In order for Virtual Nebraska imagery to be delivered
rapidly over the Internet, it is necessary to drastically lessen their size. Our challenge
is to decrease image files of 20 - 180 MB down to 50 - 100
KB! The processes used to accomplish this task involved first, resizing the image
(resampling), and then reducing the image detail through lossy data compression (JPEG).
Once the image data have been resampled and compressed, they are moved into Virtual
Nebraska on the web server. It should be noted that even though the images have been
reduced in file size, in many cases, they remain relatively large (in terms of download
time), especially if using a modem. After significant testing it was determined (in most
cases) that imagery compressed to less than 50K, suffered too greatly in quality, and
therefore, most files are larger than 50K.

Aerial Photographs

The imagery appearing in the Color-Infrared section
of Virtual Nebraska is predominatly from the National
Aerial Photography Program (NAPP). These data are cloud free and provide very
high-resolution (lots of detail) views of the landscape. The majority of the images in
this section are mosaics, meaning that two or more images have been electronically
"stitched" together to comprise one single, seamless image.

The first step in getting these data onto the web is to scan (digitize) the
photographs. All NAPP images in Virtual Nebraska are scanned at 300 dpi. Once the
images are scanned, each individual frame/picture must be geometrically rectified. Simply
put, this means the image is electronically "stretched and warped" to remove
distortions, thus making the image "map-like" in terms of positional accuracy.
Geometric rectification is necessary because raw digital images acquired from aircraft and
satellite platforms contain distortions from earth curvature, relief displacement, sensor
errors, as well as variation in sensor altitude and attitude.

After each image is geometrically rectified, an analyst must "stitch" all
individual scenes together to make one large, or composite, image. One-by-one the images
are pieced together until the mosaic is complete.

The final step to creating a mosaic is to "fine tune" the composite so that
it appears as a seamless image with no breaks or edge-matching errors. In many cases, this
process is the most difficult step of the three to accomplish. The difficulty stems from
the fact that the individual images used to generate a composite may come from different
times of the year, and in some cases, even different years. Consider the obstacles in
trying to align a Spring and Fall image. A river that was overflowing its banks in the
spring, will likely have receded and be much narrower in the fall. Likewise, a crop that
was just emerging in April or May will appear significantly different in August, thus
making it difficult to align adjoining images. Of course, there are methods that can be
used to minimize certain errors associated with image composites; however, in some cases
it is impossible to generate a perfect mosaic. Finally, after the mosaic is complete, the
composite image is prepared for the Web (resampled/compressed), as described above.

Landsat-TM

The TM data available through Virtual Nebraska have been provided by the Multi-Resolution Land
Characterization Consortium (MRLC), and subsequently processed as part of the
Nebraska Gap Analysis Project. The steps
involved in processing the TM data are similar to those of the aerial photographs
described above. In this case, however, 18 individual Landsat-TM scenes spanning the 1991
through 1993 growing seasons were used. Once the mosaic was complete, a "cookie
cutter" operation was used to define the state's boundaries. The resulting 1.3 GB
image was then subset county by county, compressed, and then moved into Virtual
Nebraska.

Historical Component

"Cross-curricular learning" is increasing in popularity in schools throughout
the country. Teachers are beginning to search for new and innovative ways to make learning
more interesting and applicable to "real life". Because remotely sensed imagery
embodies such a wealth of information (from any number of disciplines) it fits naturally
into multidisciplinary classroom activities. The imagery available through Virtual
Nebraska can be thought of as the "magnet" that pulls the various
disciplines together.

The historical component of Virtual Nebraska came to fruition soon after
"core" teachers became interested in tying space imagery together with history.
For example, there was interest in comparing old maps scribed by Lewis and
Clark with current-day satellite imagery, trying to locate remnants of the Oregon and
Mormon trials, such as wagon ruts, on aerial photography, and comparing archived photos of
Fort Atkinson with current day images. The ability to click on a satellite image, or map,
to access historic information and photographs was considered to be an excellent way for
making the data more "real" and applicable to K-12 classrooms.

After briefly researching Nebraska history, we located the Nebraska . . . Our Towns,
book series coordinated by Jane Graff of Seward, Nebraska. Following a brief meeting with
Jane, it was determined that digitizing the books and making them available through Virtual
Nebraska would be mutually benefiting. The end result is that users can now obtain
historic information for over 600 Nebraska cities. No other state in the nation has such a
comprehensive record of city history compiled under one source - it is truly
one-of-a-kind. For more information on the creation of Nebraska...Our Towns

Are the Original Data Available via CD-ROM or FTP?

In most cases, the answer is yes. However, none of the original data available through Virtual
Nebraska are pre-packaged and ready for delivery; (i.e., each request needs to be
handled separately). For this reason, you will need to contact us directly to discuss your
needs. In some cases a minimal fee may be charged to cover the cost of media and postage.
For large requests an additional processing fee may be included. Please contact Milda
Vaitkus at (402) 472-0306 / e-mail mvaitkus1@unl.edu
to discuss your requests.

Can Posters be Ordered?

Our poster products have been very popular among teachers since the beginning of the
project. They have proven to be very dynamic tools in the classroom. To order posters,
contact Milda Vaitkus at (402) 472-0306 / e-mail mvaitkus1@unl.edu. You can preview some of the sample posters
that we have available. Although only a few posters are shown, any image that is
accessible through Virtual Nebraska can be made into a poster. All of the products
are printed on a glossy photo paper using a high-quality HP DesignJet 755CM plotter. Due to the
cost of the materials we must charge for the posters, however, only for the cost of
production. Three sizes are offered: 36" x 48" / 24" x 32" / 18"
x 24" at costs of $25 / $20 / $15, respectively.

Are Virtual Nebraska Workshops Offered?

Workshops are offered to educators and others interested in learning about
remote sensing by CALMIT Through the
NebraskaView program. Our
workshops are flexible in that they can be specially tailored in length and content to fit
the needs of individual groups. For instance, we have conducted /sponsored courses ranging
in duration from 1/2 day to 5 days. We also will "take-the-show-on-the-road" to
conduct the workshops off-site. In most cases the workshops are free. However, in some
instances, registration fees may be collected to cover travel and lodging costs of the
instructors. To find out more about These workshops contact Milda Vaitkus at
(402) 472-0306 / email mvaitkus1@unl.edu

Current Activities

The goals of Virtual Nebraska- adding new components, unique datasets, tutorials and tools on
a regular basis are being implemented at CALMIT and through the NebraskaView program. On the
CALMIT and NebraskaView
websites you will find a variety of imagery available for download and many links to other
sources of data and training opportunities.